Halogenation



United States Patent HALOGENATION Albert P. Giraitis, Baton Rouge, La., assignor to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application April 2, 1952, Serial No. 280,189

4 Claims. (Cl. 260-659) Organic compounds containing two or more dissimilar halogen atoms would be very useful in synthetic organic chemistry and in industrial application. Examples of such industrial applications would include their use as solvents, particularly for dry cleaning and degreasing operations, as fumigants, as scavengers in leaded'fuels, as refrigerants, propellants, as fire extinguishing material and as flotation agents in mineralogy.

These compounds have in the past been prepared by several synthetic methods. Among these are addition of hydrogen halide to doubly bonded halogenated compounds; metathesis between an organic polyhalide and an inorganic halide containing a dissimilar halogen; addition of a mixed halogen compound such as iodine monochloride or iodine monobromide to a double bond, direct substitution halogenation of an organic halogen compound with elemental halogen and the like. In every case these methods suffer the disadvantage that either hydrogen halide or free halogen must be isolated and handled prior to the halogenation reaction. Even in the case of metathesis of an inorganic polyhalide with a dissimilar inorganic halide, preparation of the inorganic halide involves the use of elemental halogen or hydrogen halide.

An object of this invention is to provide a new method for the preparation of organic compounds containing dissimilar halogen atoms. A further object is to provide a method for preparation of organic compounds containing dissimilar halogens, which process eliminates the necesiitydof prior isolation of elemental halogen or hydrogen The present invention broadly comprises reacting an organic compound with a mixture of inorganic compounds of two or more dissimilar halogens in the presence of sulfur trioxide. In practicing my invention I obtain products derived from the organic reactant and containing two or more dissimilar halogen atoms in the molecule. The invention is applicable to organic compounds broadly. Typical of the compounds suitable for use in my process are hydrocarbons, halogenated hydrocarbons, halides, ketones, acids, both carboxylic and sulfonic, anhydrides, esters, nitriles, amides, ethers, and the like. Preferred organic reactants are the alkanes, particularly those containing not more than four carbon atoms. Besttresults are obtained with alkanes of two or less carbon atoms namely ethane and methane.

In the practice of my invention an organic compound together with sulfur trioxide is passed through a reaction zone containing a plurality of dissimilar inorganic halides, the reaction zone being held at an elevated temperature. The organic compound is converted smoothly and at a fast rate to products containing dissimilarhalogen atoms.

In other words, two or more dissimilar halogen atoms are introduced simultaneously to the organic molecule. The reaction rate is so fast that it is usually measured in a matter of seconds or a few minutes. Practice of my invention ordinarily results in-a mixture of desired products. Thus, if methane,for example, is treated under my;

2,698,348 Patented Dec. 28, I954 reaction conditions with a mixture of inorganic bromide and chloride, the organic products include chlorobromomethane, chlorodibromomethane, chlorotribromomethane, dichlorodibromomethane, dichlorobromomethane and trichlorobromomethane. Minor amounts of products containing only one halogen derivative such as methyl chloride, methylene chloride, methyl bromide, and the like, may also be present. These can be separated from the desired products by customary means such as fractional distillation.

It is possible to exercise considerable control of the process in order to produce predominantly a particular product. In general, the primary factors which control the predominant ratio of substitution of dissimilar halogens in the organic molecule are the molar ratio of dissimilar inorganic halogen compounds present in the reaction mixture, the relative rate of reactivity of the dissimilar inorganic halides, and the degree of contact of sulfur trioxides and the inorganic halide mixture. Of these, the ratio of dissimilar inorganic halide present in the reaction mixture appears to be the most important. In the example above, if the reaction is carried out with equimolar amounts of inorganic bromide and chloride, for example,

, the predominant organic products are substituted with the two dissimilar halogens in substantially equal proportions; that is, the principal product is either chlorobromomethane or dichlorodibromomethane, or a mixture of the two. If the molar ratio of inorganic bromide to chloride is of the order of two to one, then the predominant product will be substituted in substantially this ratio, as dibromochloromethane. If the ratio of inorganic bromide to chloride is approximately one to two, then the predominant organic product will be dichlorobromomethane. If the inorganic bromide to chloride ratio is approximately three to one, the predominant product will be chlorotribromomethane, and if the inorganic bromide to chloride ratio is approximately one to three, the predominant product will be trichlorobromomethane.

When more than one product containing dissimilar halogens in the same ratio is possible, the process can be controlled to yield chiefly one or the other, as desired. With methane, sulfur trioxide and an inorganic bromide to chloride ratio of approximately one to one in moles, for example, the predominant product will be either chlorobromomethane 'or dichlorodibromomethane, as stated above. When the reaction is controlled so that a relatively short contact time is used, then chlorobromomethane will predominate. With somewhat longer residence time the major product will be dichlorodibromomethane. The considerations developed in this and the preceding paragraph apply also to other organic compounds and to other inorganic halogen mixtures including mixtures of more than two dissimilar halogens.

The exact mechanism by which my invention operates is not clearly known to me. It is probable, however, that the overall transformation of organic material to polyhaloorganic product occurs according to schemes similar to the overall reaction equations indicated below.

I. 6SO3+2MX +2EX +QH2 QX X +2SO2+ HX +HX +2MES207 II. 4SO3+2MX +2EX +QH2- QX X +2SO2+ HX +HX +2MESO4 where M and E=inorganic electropositive elements, and may be the same or different X =a halogen atom X =a halogen atom dissimilar to X QH2=an organic compound QX X ;an organic compound containing dissimilar halogens HX and HX =dissimilar hydrogen halides Specific instances for these general equations, in the case of halogenation of ethane with sodium chloride and sodium bromide, are as follows:

When halogenation of a higherorder than dihalogenae tion desiredj'as 'tlie principal reaction, then correspondingly "increasmgproportions of inorganic halides should be used. When inorganic halides containing elements other than monovalent elements are used, the stoichiometry of the above equationsis slightly modified.

By: controlling the input ratios of organic reactants to sulfur trioxide the process can be made to operate to yield as the major inorganic product predominantly either sodium pyrosulfate, as in-the first equation above, or sodium sulfate, as in-the second equation. In'a preferred modificationof my invention I operate according to the first equation and produce sodium pyrosulfate. Under many ofthe'reaction conditions which I employ the latter is a liquid compound and can be so handled. It may be pumped, transferred through small diameter lines, etc. Sodium pyrosulfate can be converted to sodium sulfate and sulfur trioxide by further heating v Sulfur trioxide formed in this manner-can-be recycled to my process and sodium sulfate is a marketable material.

Any combination of two or more inorganic halides can be used according to the terms of my invention. Among the suitable mixtures are mixtures of bromides and chlorides; bromides and iodides; and iodides and chlorides as well as mixtures of bromides, chlorides and iodides. With the above combinations of inorganic reactants the products obtained will contain, respectively, bromine and chlorine; bromine and iodine; iodine and chloride and bromine, chlorine and iodine.

In addition to the inorganic halides illustrated in the equations above, the other inorganic halides generally can be employed in my process. The non-halogen portion of the molecule may be the same for both halogens or different. Illustrative examples are mixtures of sodium chloride-potassium bromide, potassium chloride-sodium bromide, sodium chloride-ferric bromide, ferric chloridepotassium bromide, aluminum chloride-aluminum bromide, ammonium chloride-sodium bromide, sodium chloride-ammonium bromide, ammonium chloride-ammonium bromide, calcium chloride-calcium bromide,-calcium chloride-lithium bromide, calcium chloride-magnesium.bro-

mide, magnesium chloride-zinc'bromide, stannic chloridepotassium bromide for the preparation of derivatives containing chlorine and bromine. 1 Forbest'results the nonhalogen portion of the inorganic halide should be selected from the group consisting of elements of groups I, II and ill" of the periodic table and the ammonium radical. Because oftheir"relative-cheapness andavailability, I especially pr'efer'to use halides-of the alkali and alkaline earth metals,'particularly sodium and calcium. In one preferred embodiment of my invention I use mixtures which include two or more compounds of the same halogen. For example, it is advantageous to use mixtures of sodium chloride-potassium chloride-ferric bromide in forming chlorobromo compounds. Use of such mixtures often-permits operation in a 'molten' halide bath at temperatures lower than if only one compound of one of the halogenswere present. 'It should beremembered that the ratio of substitution by'th'e dissimilar halogens will be determined largely by the, overall atom ratio of dissimilar halogens presentin theinorganic mixture.

For the preparation ofiorganic chloroiodo' compounds typical halidemixturesare sodium'chloride-sodium iodide, potassium chloride-potassium iodide, magnesium chloridemagnesium iodide, calcium chloride-calcium iodide, sodium chloride-magnesium iodide, lithium chloride-aluminum iodide. v

When the desired products are bromoiodo compounds the following examples are illustrative: sodium bromidesodium iodide, potassium bromide-sodium iodide, lithium bromide-sodium iodide, calcium bromide-calcium iodide, sodium bromide-calcium iodide,- aluminum bromide-ferric iodide, stannic bromide stannic'iodide, ferric bromideferric iodide. I

The following mixtures are illustrative of those which can be employed to produce materials containing three dissimilar halogens in the molecule: sodium chloridesodium bromide-sodium iodide, potassium chloride-potassium bromide-potassium iodide, calcium chloride-calcium bromide-calcium iodide, calcium chloride-sodium bromide-sodium iodide, ferric chloride-ferric bromide-ferric iodide, aluminum chloride-sodiumchloride-magnesium iodide.

In addition tothe'organic compounds illustrated above other organic compoundsfigenerally are, applicable. Ex-

amples are propane, butane isobutane, higher alkanes,

- halogenated hydrocarbons; acids;anhydridcsresterg" alderate is soslow atsuch temperatures asto makethe operation unfeasible for commercial practice. Generally, temperatures of about 250 C. are preferable for a satisfactory 'reaction rate. Theupper-limit is determined only by pyrolysis'oforganicmaterial. In many cases pyrolysis does not become prohibitively fast at temperatures of even as high as about 800 C. and therefore my invention can be used up to at least those temperatures.

20 Withmost organic compounds,ihowever, pyrolysis becomes important .in the neighborhood of 450 C'. so that I prefer not to operate above :that temperature.

My invention-is operable over-av wide "pressure-range, varying fromwell below atmospheric up '-to 'several atmospheres. For convenience and ease of operation, I ordinarily prefer to :operate near atmospheric pressure.

The 1 reaction or' contact. time of. my. process can vary within wide limits. With some of my reactants reaction is practically instantaneous and contact'times of. only a few seconds are required. With certain of'myreactants, however, particularlycompounds of 'high molecular weight and particularly where operating in the lower temperature range, somewhat longer contacttimes on the-order *ofseveral minutes are preferred. Inmany-instances'itis desirable. to recycle organic material so that only: asmallconversion per pass is realized but this has the beneficialeffect of cutting down the amount of pyrolysis .oforganic material. In this case the overall contact time can amount to many mmutes.

As stated earlier,-the halogenated compounds-obtained are usually a mixture of 1 all; the possible products with considerable control being possible in order to'produce predominantly a desired product or products; Another means of controlling-the relative amounts of products produced is by controlling the ratio of sulfur trioxide to organic reactant fed tothe reaction zone. Generally speaking, the higher the ratio of sulfur trioxide to organic reactant the higher will be the degree ofhalogenation of the organic compound. Generally speaking; for production of dihalo derivatives the ratio should be'approximately 46 parts of sulfur trioxide to'l part of organic material by volume depending on whether it isdesired to produce NazSOr or NazSzOv as the major-inorganic product. Similarly, for tri-halogenation the volume ratio of sulfur trioxide to organic reactant should beapproximately 6 9 to 1. For higher. halogenated derivatives there will be a corresponding'increase in the" ratio of sulfur trioxide to organic reactant.

The following examples will illustrate several :variations in the employment of my-invention.

Example I The reactorcomprisesa vertical tube surroundedby external heating means and having a plurality of gas inlet tubes generally in the lower portion of the reactor. ':-These inlet tubes are connected outside the reactor with means for purifying, pre-heating,- metering, and pre-mixing the gaseous reactants. Theoutlet tubeis connected to a series of condensers for condensing the liquid products. The'lower portion of the reactor is filled with a'ninert packing material upon which rests-the mixture of inorganic'halogen compounds. .]n a preferred embodiment of my invention thepointof gas introduction lies within the inert packing zone and below the inorganichalide bed. The gaseous reactants pass through the inert-packing, thence through the inorganic reactant bed and out the exit tube to thecondensers. Temperature measuring devices are: spotted at various .pointsthroughout theinorganic halogen bed.

' To such a reactor is fedamixed gas stream comprising sulfur trioxide'andethane in volume ratio of six'volumes of sulfurtrioxide to one of ethane. This'streamfispreheated to atemperature'of 350? C." The inorgani'c halide bed comprises sodium bromideand sodiumchloridecin the 'ratio'of 1.8 to 1 by weight i fie -inorganichalidemed is amass-4a maintained at-adtemperatureof 35.0 C: rThegaseous product stream is swept out throughv the. exit tube and condensed in a condenser at a temperature of approximately 75{C. The non-condensable products, chiefly unreacted ethane, continuethrough the exit line pastthe condenser and, can be recycled. The average residence time of gaseous material in the reactor is about seconds. The condensable organic products are chiefly l-chloro-Z- bromoethane and l-chloro-l-bromoethane. Also present are ethyl chloride, ethyl. bromide, dichloroethanes, dibromoethanes andtraces of triand higher halogenated products. The inorganic salt mixture is. converted chiefly to sodium pyrosulfate. Other products present in the gas exit stream are sulfur dioxide, hydrogen chloride, hydrogen bromide and unreacted ethane. Only traces of unreacted sulfur trioxide are found and no elemental halogen is observed.

Propane, butane and isobutane, when employed in this procedure, give substantially identical results. The principal halogenated organic products obtained with these materials are chlorobromopropane, chlorobromobutane and chlorobromoisobutane, respectively. Other organic compounds, such as higher hydrocarbons, halogenated hydrocarbons, acids, anhydrides, esters, ketones, acetals, and the like, give similar results when employed.

Example 11 The above experiment is repeated at a temperature of 180 C. with flow rates adjusted to provide an average residence time in the reactor of approximately 4 minutes. Substantially identical results are obtained except that there is a high proportion of triand higher halogenated products in the product mixture.

Example III Example I is repeated at a temperature of 450 C. Substantially identical results are obtained.

When the procedure illustrated in the above three examples is repeated using mixture of potassium chloridesodium bromide, sodium chloride-ferric bromide, aluminum chloride-aluminum bromide, ammonium chloridepotassium bromide, and similar mixtures, like results are obtained.

Example IV The procedure of Example I is repeated except that the inorganic halogen mixture comprises sodium bromide and sodium iodide in the ratio of 0.7 to 1 by weight. The major halogenated organic products are l-bromo-Z-iodoethane and l-bromo-l-iodoethane. Also found are ethyl bromide, ethyl iodide, dibromoethanes, diiodoethanes and traces of triand higher halogenated mixtures.

Mixtures of potassium bromide-sodium iodide, calcium bromide-calcium iodide, ammonium bromide-magnesium iodide, sodium bromide-calcium iodide, aluminum bromide-ferric iodide and similar mixtures can be used in this procedure with similar results.

Example V Ethane is treated with sulfur trioxide and a mixture of ferric chloride and zinc iodide in the ratio of 0.5 to 1 according to the procedure of Example I. The principal organic products are chloroiodoethanes.

Example VI Ethane is treated with sulfur trioxide and a mixture of sodium chloride and sodium bromide in the ratio of 1.1 to 1 at a temperature of 400 C. The ratio of sulfur trioxide to ethane fed to the reaction zone is 9 to 1 by volume. The principal organic halogenated products are dichlorobromoethanes.

Example VII Methane is processed according to the procedure of Example I except that the temperature of reaction is 600- 700 C. Contact time is approximately 10 seconds. The principal halogenated organic product is chlorobromoethane.

6 Example VIII Example VII is repeated except that the contact time is increased to about2 minutes. The principal organicproduct is dichlorodibromomethane.

Example IX Example VII is repeated except that the ratio of sodium bromide to sodium chloride is 0.9 to l. The predominant organic product is dichlorobromomethane.

Example X Example VTI is repeated except that the ratio of sodium bromide to sodium chloride is 3.5 to l. The predominant organic product obtained is chlorodibromomethane.

Example XI Ethane is treated at 250 C. with sulfur trioxide and a mixture of sodium chloride, sodium bromide and magnesium iodide. Organic products containing all three halogens are obtained.

Example XII Acetone is processed according to the procedure of Example XII. The principal halogenated organic product obtained is chlorobromo acetone.

This procedure can be applied equally well to other compounds such as acetophenone, diethyl ketone, propiophenone, methyl isobutyl ketone, and the like.

As stated above, other organic compounds can be processed in addition to those used for purpose of illustration. For example, ethyl chloride can be converted by use of the various procedures illustrated to yield dichloro bromoethanes, dichloroiodoethanes, dichlorofiuoroethanes, fiuorobromochloroethanes, and the like. Acetic acid may be converted to chlorobromoacetic acid, difluoroiodoacetic acid, dichlorofluoroacetic acid. Other organic products may be treated to yield the desired products. Thus, n-hexanoic acid, acetic anhydride, butyric anhydride, ethyl acetate, methyl butyrate, methylethylketone, valeraldehyde, di-n-butyl ether, ethyl ether, nitropropane, acetal, methylal, etc. may all be treated with any of the inorganic halide mixtures mentioned herein to yield the corresponding halogenated products.

There are other physical means of carrying out my invention in addition to those disclosed herein. For instance, the reaction can be carried out in molten sodium pyrosulfate medium, or continuously, using a fluidized bed technique of contacting solids with gases, or in a mixture of inorganic halides in the molten state.

I claim:

1. A process of producing halogenated alkanes containing dissimilar halogens and metal sulfates, comprising treating in a reaction zone a mixture of dissimilar solid metal halides containing dissimilar halogen atoms selected from the class consisting of alkali metal chlorides, alkali metal bromides, alkaline earth metal chlorides, and alkaline earth metal bromides with a saturated hydrocarbon at a temperature of from 250 to 450 C. in the presence of sulfur trioxide, the sulfur trioxide being in proportion of from about 4 moles to about 9 moles to each mole of said alkane; separately withdrawing a gaseous product stream and a non-gaseous product stream from the reaction zone, the gaseous product stream comprising halogenated alkane containing dissimilar halogens, sulfur trioxide, and hydrogen halide, and the non-gaseous stream comprising metal sulfate; and recovering halogenated hydrocarbon containing dissimilar halogen atoms from the gaseous product stream.

2. Process of claim 1 in which the saturated hydrocarbon is ethane.

3. Process of claim 1 in which the mixture of dissimilar amaze:

solid metal halides is azm'ixture ofzrsodium bromide and sodium chloride. I p 7 4; A process of producing. halogenated ethane contam-- ing dissimilar halogens and sodium. sulfates, comprising product stream andaninorganictsalt mixture: from there action zone, and recovering halogenated ethane containing drssrmllar halogens from the gaseous product stream.

Number UNITEDI STATES .PATENTS Name Date Grauli .---4 Nomi-26, 1912 :Brooks ettali July 31', 1917 Lacy Oct: 9, 1917: :Nafash IJuly--6, 11937 I-lerr .10ct;' .114; 1941 zKharaschzet al. -'Nov. =l 7,1942' IMGIZ'. Dearl -1947 Hixsonzet'xal; May 22; 1951 

1. A PROCESS OF PRODUCING HALOGENATED ALKANES CONTAINING DISSIMILAR HALOGENS AND METAL SULFATES, COMPRISING TREATING IN A REACTION ZONE A MIXTURE OF DISSIMILAR SOLID METAL HALIDES CONTAINING DISSIMILAR HALOGEN ATOMS SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL CHLORIDES, ALAKLI METAL BROMIDES, ALKALINE EARTH METAL CHLORIDES, AND ALKALINE EARTH METAL BROMIDES WITH A SATURATED HYDROCARBON AT A TEMPERATURE OF FROM 250 TO 450* C. IN THE PRESENCE OF SULFUR TRIOXIDE, THE SULFUR TRIOXIDE BEING IN PROPORTION OF FROM ABOUT 4 MOLES TO ABOUT 9 MOLES TO EACH MOLE OF SAID ALKANE; SEPARATELY WITHDRAWING A GASEOUS PRODUCT STEAM AND A NON-GASEOUS PRODUCT STREAM FROM THE REACTION ZONE, THE GASEOUS PRODUCT STREAM COMPRISING HALOGENATED ALKANE CONTAINING DISSIMILAR HALOGENS, SULFUR TRIOXIDE, AND HYDROGEN HALIDE, AND THE NON-GASEOUS STREAM COMPRISING METAL SULFATE; AND RECOVERING HALOGENATED HYDROCARBON CONTAINING DISSIMILAR HALOGEN ATOMS FROM THE GASEOUS PRODUCT STREAM. 